(original) (raw)

On Fri, Feb 3, 2012 at 5:52 PM, �ric Araujo <merwok@netwok.org> wrote:

Hi Matteo,

Now setup.py will rebuild all every time, this is because the policy of
newer\_group in build\_extension is to consider 'newer' any missing file.

�

Here you certainly mean �older�.

No, and this is the problem: newer\_group(depends, ext\_path, 'newer'))

if (some dep is newer than the target): rebuild
�

[...] Can someone suggest me the reason of this choice

�

distutils� notion of dependencies directly comes from make. A missing
(not existing) target is perfectly normal: it�s usually a generated file
that make needs to create (i.e. compile from source files). �In this
world, you want to (re-)compile when the target is older than the
sources, or when the target is missing.

Here is a simple Makefile that has the behavior I was expecting from distutils too:

$ cat Makefile
all: missing.dep
�� echo "Done!"

$ make
make: *** No rule to make target `missing.dep', needed by `all'.� Stop.

So here your extension module is a target that needs to be created, and

when distutils does not find a file with the name you give in depends, it

just thinks it�s another thing that will be generated.

So, if I understand correctly, starting today a better name could be 'generates' instead of 'depends'?

This model is inherently prone to typos; I�m not sure how we can improve

it to let people catch possible typos.

Yes, perhaps the name of the list and the explanation in the docs are both a bit confusing:

http://docs.python.org/distutils/apiref.html#distutils.ccompiler.CCompiler.compile

depends, if given, is a list of filenames that all targets depend on. If a
source file is older than any file in depends, then the source file will be
recompiled.

Can this be a better explanation? "If a
source file is older than any file in depends {+or if some depend is missing+}"

Cheers

--
Matteo Bertini
http://www.slug.it/naufraghi